Coccidial oocysts were detected in 35% of 445 cattle in four medium-scale and 20 small-scale dairy farms in Morogoro municipality, Tanzania. The highest prevalence (56%) was observed in animals aged between 5 and 18 months, whereas lower prevalences were observed in calves (29%) aged between 12 days and 4 months and adults (30%). No coccidial oocysts were detected in calves less than 12 days old. The oocyst output was high in calves, followed by weaners; adults had the lowest oocyst output. The number of oocysts per gram of faeces was significantly higher (P < 0.001) in diarrhoeic animals than in non-diarrhoeic animals, and more so in young calves. Eimeria species infecting the animals included Eimeria bovis (68%) and Eimeria zuemii (57%), Eimeria ellipsoidalis (25%), Eimeria cylindrica (23%), Eimeria aubumensis (22%), Eimeria alabamensis (12%) and Eimeria subspherica (5%). Mixed infections involving two or three species were common. Our findings indicate that eimeriosis is common in cattle in Morogoro municipality. Published by Elsevier Science B.V.